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Cancer Staging and Lung Cancer Prognosis

The stage of the tumor has a major impact on lung cancer prognosis. Cancer staging is the process of determining tumor size, growth rate, possible metastasis, lymph node involvement, treatment options and prognosis. While a biopsy provides proof of the presence and type of cancer, further testing is required to determine the stage of the disease.

Diagnostic Imaging

Initial diagnosis of lung cancer may have included the use of diagnostic imaging. Computed tomography and other imaging tools are also used in cancer staging. More than one type of test may be required, especially if metastasis is suspected.

Computed Tomography: Also known as a CAT or CT scan, computed tomography uses x-rays to take multiple pictures of the lungs and generate a 3-dimensional computer image.

Magnetic Resonance Imaging: Magnetic resonance imaging (MRI) uses powerful magnets to create radio waves. The radio waves change slightly depending on the type of tissue they are aimed at, and recording these changes allows computers to build 3-dimensional images.

Positron Emission Tomography: While magnetic resonance imaging and CAT scans create images of the lungs, positron emission tomography (PET) allows doctors to view the lungs at work. A mild radioactive compound that is absorbed by different types of cells at different rates is either injected or swallowed. Positron emission tomography takes up to an hour to perform, but provides valuable information about lung function.

Radionuclide Scanning: In order to determine if metastasis to other organs has occurred, a radionuclide scan may be ordered. The scan uses radioactive materials to detect cancerous cells.

Mediastinoscopy: In a mediastinoscopy a hollow tube with a light at the end is used to examine the chest cavity and lymph node system for signs of metastasis. The tube is inserted through a small surgical incision in the neck. If additional biopsy samples are required, samples can be retrieved during the mediastinoscopy.

TNM Staging and Lung Cancer Prognosis

The severity of non small cell lung cancer (NSCLC) is determined using TNM staging. The staging is divided into three categories. T stands for tumor, N for lymph node, and M for metastases.

Tumor (1-4): T1 is a tumor less than three centimeters; in T2 it is larger than three centimeters; T3 is a tumor of any size that passes into the chest cavity, and is operable; T4 is inoperable.
Lymph Node (0-3): N0 is no lymph node involvement; N1 involves the lymph nodes in the lungs; N2 involves the nodes in the chest, esophagus or windpipe; in N3 those above the collarbone are involved.
Metastases (0 or 1): M0 is no indication of metastasis; in M1, disease has spread to other organs.

NSCLC staging examples might read T1N2M0, or some other combination of the above stages. The TNM data gathered is then used to divide lung cancers into four stages, the higher the stage the poorer the five-year prognosis:

Stage 1: Subdivided into 1A and 1B. The tumor is small, contained, and surgically removable with no lymph node involvement. Prognosis of 1A is 67 percent. Prognosis for 1B is 57 percent.
Stage 2: Subdivided into 2A and 2B. The tumor remains operable, but malignant cells have spread to lymph nodes around the lung. Prognosis for 2A is 55 percent. Prognosis for 2B is 38 percent.
Stage 3: Subdivided into 3A and 3B. Additional lymph node invasion has occurred, and the tumor has spread to the lung lining or into the chest cavity. Surgery may remain an option, with radiation therapy and chemotherapy as other possible alternatives. Prognosis for 3A is 23 percent. Prognosis of 3B is 5 percent.
Stage 4: Metastasis to other organs has occurred. Treatment options are confined to palliative care, and prognosis is poor (1 percent). Life expectancy is less than one year.

Small Cell Lung Cancer Staging and Prognosis

Small cell lung cancer staging differs from the NSCLC TNM staging. There are three categories of SCLC: limited, extensive, and recurrent. The limited stage has no evidence of metastasis. The extensive designation means that the cancer has spread to other organs. Often limited SCLC is treated with the assumption that metastasis has occurred, just to be safe.

Two-year prognosis for limited SCLC is twenty percent and for extensive disease five percent. The average life expectancy for someone with recurrent SCLC is two to three months.

Resources

Busick, N. P., Fretz, P. C., Galvin, J. R. & Peterson, M. W. (revised 1999). Staging of small cell and non-small cell lung cancer. University of Iowa Virtual Hospital.

Cancer Research UK. (updated 2001). Stages of lung cancer.

National Cancer Institute. (updated 2002). What you need to know about lung cancer: Staging the disease [NIH Publication No. 99-1553].

Warren Grant Magnuson Clinical Center & National Institutes of Health. (2000). Procedures/diagnostic tests: Positron emission tomography (PET) scan; Diagnostic.

Ruckdeschel, J.C. Lung cancer staging: Its definitions and significance. Myths and Facts About Lung Cancer: What You Need to Know. PRR, Inc. Melville, NY, (1999).

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